Electron tube and circuit therefor



H. F, ELLIOTT 9 3 June 3@, 1936.

ELECTRON TUBE AND CIRCUIT THEREFOR Filed June 25, 1932 3 Sheets-Sheet 1 i 2 KN E 5 4 i, ,4" A a INVENTOR Hara/d f. 5275032 ATTORNEY W JQX J1me 3(0), 1936. H. F. ELLIOTT ELECTRON TUBE AND CIRCUIT THEREFOR Z Sheets-Sheet 2 Filed June 25, 1932 E nis R m M E M 7 w BY Hi3 ATTORNEY June 36), 11.936. H. F ELLIOTT ELECTRON TUBE AND CIRCUIT THEREFOR 5 Sheets-Sheet 5 Filed June 25, 1932 v Z-Jaro/d E Eifzbii BY HIS ATTORNEY W PW Patented June 31 1936 UNITED STATES .eArsnr OFFICE 16 Claims.

My invention relates to electron devices such as are utilized for amplifiers, detectors, oscillation generators, frequency multipliers and other purposes in the electrical arts, and particularly to electron tubes and circuits for such devices.

An object of my invention is to provide electron tubes and. circuits whereby many of the functions of such devices may be carried out more elfective- 1y, more efficiently, and more simply than by means heretofore employed. Another object is to reduce the amount of apparatus required and consequently to effect savings in the size and cost of such devices.

Reference is made to my co-pending applications, including the following: application Serial No. 605,185, filed April 14, 1932 for Electronic detecting and amplifying systems; application Serial No. 605,186, filed April 14, 1932 for Electronic tubes; application Serial No. 606,613, filed April 21, 1932 for Receiving systems; application Serial No. 606,614., filed April 21, 1932 for Oscillators and modulators; application Serial No. 607,857, filed April 27, 1932 for Modulators and de-modulators.

In these co-pending applications, I have shown electron tubes comprising a. cathode, an anode, and two or more symmetrically arranged grids, together with circuits whereby such tubes may be applied to useful commercial and scientific purposes, and particularly to such devices as amplifiers, detectors, oscillation generators, frequency multipliers, and the like. In my invention described hereinafter, I disclose several new forms of electron tubes comprising two cathodes, one or more anodes, and one or more grids, together with circuits whereby results similar to those of the devices and methods of the aforementioned co-pending applications may be attained. The new tubes also have advantages distinctly their own in that they may be utilized to carry out certain functions not attainable with tubes heretofore available.

Referring to the drawings, Figs. 1 to l inclusive show several typical forms of tubes constructed in accordance with my invention. Fig. 5 shows circuits for a complete broadcast receiver embodying one form of my invention. Figs. 6 to 13 inclusive show circuits of other typical applications in accordance with my invention.

Referring specifically to Fig. 1, the electron tube here illustrated comprises two cathodes, l and 2, which are preferably of the unipotential type heated directly as by heaters 5 and 6. The two cathodes are surrounded by a control grid 3 and an anode 4. For certain applications, as described hereinafter, it is desirable to place an auxiliary anode 1 around extended portions of the two cathodes, as shown.

For purposes of clarity, no supporting structures on other mechanical details are included in the drawings of the tubes of Figs. 1 to 4. However, it will be understood that the tube elements may be suitably supported and enclosed in suitable evacuated containers, such as the glass bulb 8 shown in Fig. 1. Suitable connections for the elements may be provided as for example by leads, such as 9, connecting to terminals, as H, in base ID, or to cap l2 on top of the bulb.

In the tube illustrated in Fig. 2, the elements comprise two cathodes, l and 2, which are surrounded by two control grids, 3 and i3, and an anode 4. An auxiliary anode may be provided when desired; this may take the form of an electrode l' surrounding extensions of the cathodes, as in Fig. 1, or may be an electrode placed between the two cathodes, as shown in Fig. 2.

The tube ilustrated in Fig. 3 consists of two cathodes, I and 2, surrounded by a control grid 3, a screen grid I4, a suppressor grid I 5, and an anode 4. If desired, the screen or suppressor grid may be extended so as to shield the control grid from the anode, as in commercial tubes now in common use.

A further form of tube is shown in Fig. 4, wherein a plurality of cathodes are employed. In the case illustrated, six cathodes, Iii-2| inclusive, are shown. These are symmetrically arranged and surrounded by a control grid 3 and anode 4. An auxiliary electrode 22 may be placed at the center of the circle or ellipse upon which the cathodes are spaced.

The objectives of the various electrode arrange ments outlined above are most readily illustrated by means of circuits showing typical applications which will now be discussed.

The circuit of Fig, 5 represents a typical superheterodyne type of broadcast receiver adapted to embody the principles of my invention. Tube 23 is an R. F. amplifier which serves to amplify incoming signals at the frequency at which they are received. Tube 24 is a detector which serves to mingle the amplified signals with heterodyne currents supplied by oscillation tube 28, thereby changing the signals to an intermediate frequency. Tube 25 serves to amplify the intermediate frequency signals delivered by detector 24. Tube 26 is a second detector which serves to demodulate the amplified intermediate frequency signals and convert them into audio frequency signals. Tube 21 serves to amplify the audio frequency signals and deliver them to the loud speaker. Tube 29 is the usual rectifier which serves, together with the filter comprising capacitors 3B3ll'3il, and inductors 3| and 32, to supply direct current potentials of a few hundred volts for the operation" of the various tubes and circuits. r

Inasmuch as all of the tubes and circuits, eX-

' cept those relating particularly to the second detector 26, are typical of commercial superheterodyne broadcast receivers in'common, use, only the features and functions of tube 23, and. its associated circuits will be described in. detail here.

Tube 26 is shown in Fig. 5 as comprising two cathodes, I and 2, a control grid 3, and an anode 5. These electrodes may be arranged in a manner similar to that illustrated in Fig.1. Alternatively, tubes similar to those of Figs. 2, 3 and 4 may be employed by making suitable simple changes in the circuits, as will be apparent from the discussion hereinafter. The arrangement shown inFig. 5 and, in fact, in all of the figures hereof, is given merely as a typical illustration,

and is not to be taken in'a limiting sense'since my invention, as defined in the appended claims,

hasa much broader scope than can be illustrated fully in a group of typical figures. such as are given herein.

' Referring specifically tothe circuits associated with tube .25 in Fig. 5, the secondary winding .33, of the intermediate frequency transformer 33-34, is preferably provided with a center, tap as shown. Cathodes I and 2 are preferably connected to opposite terminals" on winding 33. From the center tap a-connection may be made to the con.- trol grid 3 through the medium of load resistor 35; sometimes called a grid leak. The latter may be shunted by a capacitor 36 of the order of 50 'to l50'micromicrofarads, or 36 may simply represent the stray capacitances of the system. In the arrangement shown in'Fig. 5, the center tap on coil 33:.i's connected directly to the mainnegative bus 37 which maybe grounded as shown.

The anode 4 of tube 26 is connected to the positive bus 38 through resistor 39. Choke 40 and by-pass capacitorAl may be provided to: filter radio frequency currents the anode, circuit. Alternatively, these may, be omitted. if: operating conditions permit, as is usually the case, since the balanced arrangement of tubeel'ements automaticallysuppresses radio frequency currents in the anode circuit. The audio frequen'cy component of potentials across resistor 39 may be applied to tube .Z'lthrough. capacitor 42 and potentiometer 43 which may serve as a manual volume control.

'aicrossresistor' 39 in the-anode circuit.

Inoperation, the amplified intermediate frequency. signals which appear across inductor 33 are ,applied equally and oppositely tothe twov cathodes, I and 2. .Whenever either of. these is which thus appear across resistor 35 are applied to the grid (land to the two cathodes; land 2,

in iparalleli. The two cathodes, the grid and the anode then serve'as'an audio frequency amplifier whereby-the pulsations in resistor 35 are amplified and? appear as audio frequency potentials tive with respect to the cathodes.

The two. cathodes and the It will be evident that the rectification process causes grid 3 to assume a charge which is'nega- This negative charge is proportional to the amplitude of the carrier and may be utilized for the purpose of automatically controlling the amplification in tubes 23, 24 and 25. This may be carried out by connecting grid 3 to the grid circuits of tubes 23, 23 and 25 through the medium of suitable filter resistors and by-pass capacitors such as resistors 44, 45, 46 and 41 and capacitors 48, 49, 53 and El.

ers having automatic volume control and therefore need not be described further here.

It'will be evident from the foregoing that tube of suitable potential as will be'readily understood by those conversant with electron-tubes.

This system of connections is similar to those" ordinarily employed in commercial receiv- Alternatively, a tube with more than two cathodes, such as is shown in Fig. 4 may be utilized.

Ihe cathodes may be connected in two parallel groups, as shown in Fig. 6, or may be connected individually to suitable points of balanced potentialsand opposing phases in the input circuit.

The connection of the two or more cathodes to points of equal potentials and oppositephases serves two purposes: (1) full wave rectification is provided, and (2) radio frequency currents are substantially excluded from the anode circuit.. This latter feature is important since it conserves the entire power output'capacity of the tube for useful audio frequency energy.

Fig. 6 shows an alternative arrangement for the elements and circuits associated with the detector tube 23 of Fig.5. By way of example; 'the tube in Fig. 6 is shown as comprising six cathodes, i3-2l inclusiveQ These may be connectedin two parallel-groups with alternate cathodes connected tothe top and bottom of coil 33 respectively; Another feature of Fig. 6' is the utilization of the auxiliary anode l in the circuits associated with the automatic volume control system which comprises resistor 34, capacitor 8, and the remainingv system connected to the volume control buss 52, as inFig. 5;. When the.

arrangement'shown in Fig, 6 is employed, the cathode return circuit leading from the center tap on coil 33 is preferably connected through one or more filter resistors, as 5'i58, via lead 33 to' a point in the power supply system which is negative with respect to the ground bus by a potential of the order of volts. The anode is preferably connectedthrough a transformer or choke, as 62, via lead 64, to a point which is 50 to 100 volts positive with respect to the ground bus. When such a system is employed, the oathodes will floatat a potential of 10 to 40 volts positive with respect to ground when no signals are present. When a signal is tuned in, the negative charge which accumulates on grid 3 as a re sult of rectification causes the current in the anode-cathode circuit, and in resistors 5l'58, to be reduced. This causes the cathodes more nearly to approach the potential'of lead 63, which, as aforementioned, is preferably-about 100 volts negative with respect to ground. When a carrier is received which causes the cathodes to become negative with respect to ground, electrons will be attracted to the auxiliary anode 1, current will flow in resistor 59, and a negative charge will consequently be placed upon the automatic volume control bus 52. The point at which this automatic control action takes place may be adjusted by suitably proportioning the potentials applied to leads 63 and 66 and by adjusting the resistors 51-58. Such an arrangement has the advantage of not attenuating weak signals and of holding strong signals to substantially constant output. The potentials available for automatic control are greater than those of Fig. 5 since in Fig. 6 advantage is taken of the amplifying function of the tube in deriving the volume control potentials.

The arrangement of Fig. 6 is subject to many variations. For some conditions of operation it may be desirable to connect lead 53 of the volume control system to point 55 instead of point 54, as shown. Under these conditions the unidirectional action of the auxiliary anode is dispensed with and the volume control bus 52 receives whatever potential appears on the cathode circuit at point 55. If this is made positive with respect to ground, the consequent positive charges on the grids of the preceding amplifier and/or detector tubes may cause a blocking action in the latter. This may cause the receiver to be insensitive to weak signals and static disturbances but to remain receptive for signals suiiiciently strong to overcome the positive charge and cause the grids again to become negative. The point at which this action occurs can be controlled by proportioning the potentials applied to leads 6364 and by suitably adjusting the resistance of Ell-58.

Another alternative arrangement of Fig. 6 is to connect lead 53 to point 56 in which case the potentials applied to the automatic control bus 52 are the sum of the potentials across resistor 35 and capacitor 66. The latter, together with capacitors t l, and 66, serve to filter fluctuations in the power supply and prevent them reaching the anode-cathode circuit of the tube The various circuit combinations outlined above for Fig. 6 may be applied to any of the tubes illustrated in Figs. 1 to 4 inclusive by suitable variations in connections and by supplying suitable potentials for the screens, if used, as will be apparent to those skilled in the use of electron tubes.

Fig. 7 shows an arrangement whereby the circuit principles outlined above for Fig. 6 may be applied to a system wherein it is desired to tune inductor 33 by means of a capacitor having one side grounded, such as is shown at 67. In this case, an impedance such as choke 58 may be used to allow the center tap on inductor 33 to seek an electrical center for radio frequency currents which is midway between the radio frequency potentials of cathodes l and 2. Audio frequency components may be by-passed by capacitor 69.

Fig. 8 shows an arrangement suitable for use with tubes of the type shown in Fig. 2, having two cathodes and two grids symmetrically arranged. Such a system may be applied in a great variety of ways. As one example, secondary inductors 33 and it may be coupled to primary inductor 34 and the electrical centers of the former interconnected through resistor 35. Potentials for automatic volume control may be obtained from the drop across resistor 35 as shown in Fig. 8 or via an auxiliary anode system as shown in Figs. 6 and 7.

Figs. 9 and 10 show typical arrangements whereby tubes of the type shown in Figs. 1 to 4 may be utilized as modulators or demodulators. Signal or carrier currents to be modulated or demodulated may be applied to the input circuits 'H'l2 and l31 in any convenient manner. The resultant output currents will appear in circuits 5-?5. Suitable sources of anode and grid potentials are shown at ll and F8. With the arrangement shown in Fig. 9, neither of the signals or carriers applied to the input circuits ii-l2 and FE-"Hi appears in consequential volume in the output circuit 15-45. Substantially the entire output capacity of the tube is therefore available for useful currents. With the arrangement shown in Fig. 16, the input applied to circuit l3'i5 does not appear in volume in the output circuit l5l6, while the input from circuit 'H12 may be allowed to appear in the output or may be suppressed by suitable filtering arrangements.

Fig. 11 shows in outline circuits suitable for performing the function of frequency multiplicaton with tubes of the type of Figs. 1 to 4. Input currents of one frequency may be applied through suitable circuits, as 198il and output currents of a multiple thereof may be delivered through suitable output circuits, as iii-82. Impedances, as 83 and 84, may be utilized to select and intensify the particular frequency which it is desired to deliver.

Fig. 12 shows a circuit arrangement whereby tubes of the type illustrated in Figs. 1 to 4 may be utilized as self neutralized amplifiers. The input circuits 85-86 may be connected to the cathodes l and 2 in balanced relation, as shown, and the cathode heaters may be arranged so that an unbalance exists in the electron emission from the cathodes. For example, one heater 5 may be left unconnected and another 6 may be supplied with suitable potential for normal operation, as from a transformer. Suitable positive and negative potentials for the anode, screen and grid circuits may be supplied in any convenient manner as from batteries or a power supply unit. With the arrangement shown there will be substantially no electrostatic coupling through the tube between the input circuits 8586 and the output circuits 3'l-38. By suitable shielding, electromagnetic coupling between the latter may be avoided, as will be understood. The only coupling between the circuits will therefore be the unidirectional amplifier coupling through the electron stream between cathode 2 and anode 4.

Fig. 13 shows an arrangement whereby tubes of the type of Figs. 1 to 4 may be utilized to per-- form the combined functions of generating oscillations and modulation or demodulation. Oscil- C lations may be generated by suitably coupling an input circuit, as 89, with an output circuit as through the medium of feed back coil 94. Sig-- nals to be modulated or demodulated may be applied to input circuits 9U9l and the resultant currents delivered through output circuits 92-433.

It will be evident to those skilled in the fields of communication and other electrical arts that many other variations and adaptations of the tubes, circuits and principles illustrated may devised. I do not limit myself to the examples given herein but claim as my invention the apparatus and methods defined in the appended claims.

What I claim is: I

1. A radio receiving apparatus comprising in combination, an electron tube having two cathodes, an anode and a grid, asource'of direct current potential entirely external to the tube, an

7 impedance, input connections applying carrier 'frequency signal potentials to the two cathodes in phase opposition, input connections applying audio frequency signal potentials to the grid and two cathodes in phase addition, and an output circuit including the two cathodes, the anode, said source of potential and said impedance.

2. A radio receiving apparatus in accordance with claim-1, with the addition of an auxiliary anode associated with said 'two cathodes and an auxiliary signal rectifier circuit comprising an impedance, the auxiliary anode and the cathodes. .3. A radio receiving apparatus in accordance with claim 1, with the addition of a screen grid in the tube and a biasing potential source interconnecting the'screen' and cathodes.

'4. A radio receiving apparatus in accordance with claim 1, having in addition thereto a screen grid and a suppressor grid within the tube and a'source of potential and connections between the cathodes and grids.

5. A radio receiving apparatus comprising two adjacent electrically symmetricai cathodes, an

anode enclosing the two cathodes and forming a single electron discharge space and two grids symmetrically arranged between the cathodes and anode, in combination with an external source of potential and circuit applying different signal potentials to the said cathodes and grids.

.6. A. radio receiving apparatus in accordance common potential in the power circuit.

7 8. A radio receiving apparatus comprising in combination, an electron tube having a plurality of cathodes, an anode, and at least one grid, an

impedance, a source of direct current potential derived from means entirely external to the tube, input connections for applying addititive potentials to the cathodes and a grid, input connections for applying opposing signal'potentials to the cathodes, and output connections including 5 the cathodes, the anode, said impedance and said source of potential.

9. A radio receiving apparatus in accordance with claim 8, having in addition thereto an auxiliary electrode symmetrically placed with respect to said cathodes, and a source of potential and automatic gain control circuit interconnecting said electrode and the cathodes.

10. A radio receivercomprising in combination with input'and output circuits, an electron tube 1 comprising two cathodes, an anode and a grid,

an impedance and asource of direct current external to the tube, connections in the input circuit applying, signal potentials of one frequency to V the grid and two cathodes in phase addition while signal potentials of another frequency are applied to the grid and two cathodes in phase opposition,

and connections in the output circuit including the cathodes, the anode, said impedance and the source of potential.

11. A radio receiver comprising an electron tube for amplification and detection, in combination with apparatus external to the tube and provid. ing input and output circuits, said tube being utilized for automatic amplification control and comprising two cathodes, an anode and a grid, an impedance, and .a source of direct current externai to the tube, the input circuit including the cathodes, a grid and connections applying audio frequency signal potentials to the grid and two cathodes in phase addition, radio frequency 'signal potentials to the cathodes in phase opposition and rectified control potentials to said external apparatus, and said output comprising the anode, the cathoda'said source of potential and impedance. e 1

12. In combination in a superheterodyne receiver having an electron tube as an oscillator and detector, said tube comprising two cathodes, an anodeand a grid, an impedance and a source of potential, an input circuit applying signal potentials of one frequency to the grid and two cathodes in phase addition and signal potentiais of another frequency to the two cathodes in phase opposition, and output circuit connections 7 including the cathodes, theanode, said impedance and said source of potential.

13. A superheterodyne receiver having an electron tube as an oscillator and detector, said tube comprising two cathodes, an anode and a grid, an impedance and a source of potential, input circuit connections applying signal potentials of one frequency to the grid and two cathodes phase addition and signal potentials of another frequency to the two cathodes inphase ,opposi tion, and output circuit connections including the cathodes, the anode, said impedance and said source of potential. 14. A superheterodyne receiver having an electron detector tube comprising two adjacent cathodes, at least one grid and at least one anode in vco-operative relationship surrounding both cathodes in a single electron discharge space, input charge space, input circuits applying a plurality of signal frequency potentials to the cathodes and at least one cold electrode, and an output circuit including the cathodes, a cold electrode, an impedance and a source of direct current energy.

16. The combination with a signal circuit, an

electron tube havingja pluralityof cathodes, and

an electron current circuit including the cathodes and source of direct current entirely external to the tube, of means for utilizing the cathodes 'in one phase relation for one signal function in said circuitand means for utilizing them in another phase relation for another signal function in said circuit.

' HAROLD F. ELLIOTT. 

